Wurtzite GaN films irradiated at room temperature with 308 MeV 129Xe35+ or 230 MeV 208Pb27+ ions have been studied by atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). The three-dimensional AFM images showed that swellings of the GaN films were caused by the ion irradiations at very low fluences. In comparison with the Xe ions, the Pb ions led to a much more pronounced swelling. The XPS results indicated that after the Xe and Pb irradiations, the contents of Ga and N dangling bonds in the GaN increased, and the contents of Ga-O and N-O bonds in the surface layer also increased. In the case of the Pb irradiation, a peak associated with the defect of interstitial N was detected in the N 1s core-level spectrum, implying the formation of N2 bubbles close to the GaN surface. However, no homonuclear Ga-Ga bond was found according to the related Ga 3d spectrum. The dramatic experimental results are discussed and the distinct difference of irradiation damages in GaN induced individually by the Xe and Pb ions is analyzed.

GaSe4 films were prepared using thermal evaporation technique onto glass and Si substrates. GaSe4 in both ingot and thin films was studied by hot probe procedure indicated n-type semiconductor. The conductivity activation energy (ΔE) decreased from 0.414 to 0.365 eV with the increase in film thickness from 90 to 500 nm. Investigation of the heterojunction n-GaSe4/p-Si by using characteristics indicated good rectification with rectification ratio of 48 at room temperature and at V = ±1.6 V. The ideality factor decreased from 2.2 to 2.13 while the reverse saturation current decreased from 8.3 × 10−7 A to 3.27 × 10−7 A by the temperature rise from 310 to 363 K. For lower and higher values of applied voltage, Pool-Frenkel and Schottky coefficients were 2.2 × 10−5 and 0.7 × 10−5 eV m−1/2, beside that, Schottky barrier height was found to be 0.4 eV. The thermionic emission mechanism occurs in the low forward voltage range but in the high forward region, the space-charge-limited current (SCLC) controlled by a single trap level is the dominant mechanism. In the reverse direction the Poole-Frenkel mechanism is the operating mechanism. Analysis of C-V characteristics of Au/n-GaSe4/p-Si/Al heterojunction gives the values of effective density of states (N) of 2.4 × 1034 cm−3 and the built-in voltage (Vb) of the junction is 0.78 V.

Nano-imprint lithography (NIL) is one of the most promising patterning technologies, in which nano- and micro-patterns are fabricated on various substrates. NIL provides high throughput and low cost in fabricating nano-structures due to its simple process and allows resolution below 10 nm without issues of light diffraction with conventional lithographic techniques. Its patterning mechanism is based on mechanical deformation of a polymer resist, which is simply done by pressing with a mold. This patterning mechanism also enables inorganic and organic-inorganic hybrid materials to be directly patterned by NIL. This article covers the recent progress of NIL-based direct patterning techniques and their applications to devices. Recently, functional nano- and micro-patterns have been applied to various electronic devices for the enhancement of overall performance. Fabrication methods of these devices are difficult using convention lithographic techniques due to complex processes, high cost and low throughput. Direct NIL technique using functional resist can simply fabricate functional nano- and micro-structures and thus can be usefully applied to various industries.

The present work reports the temperature and frequency dependence of dielectric constant (ε′) and dielectric loss (ε′′) in binary Se98M2 (Ag, Cd and Sn) alloys. The measurements have been made in the frequency range (1–500 kHz) and in the temperature range 297–345 K. The values of dielectric constant (ε′) and dielectric loss (ε′′) were found to decrease with frequency and increase with temperature. The maximum barrier height Wm is calculated from dielectric measurements according to the Guintini equation. The results indicate that the dielectric dispersion exists in the present glassy systems in the above frequency and temperature range.

In the present paper, we have theoretically predicated some significant physical parameters, i.e., coordination number, constraints, density, molar volume, cohesive energy, heat of atomization, etc., for glassy Se80Te20 and glassy Se80Te10M10 (M = Cd, In, Sb) alloys. A theoretical study of the glassy Se80Te20 and glassy Se80Te10M10 (M = Cd, In, Sb) alloys reveals that there is a significant change in the structural environment of the system due to rigidity percolation.

De Haas-van Alphen oscillations of the organic metal θ-(ET)4ZnBr4(C6H4Cl2) are studied in pulsed magnetic fields up to 81 T. The long decay time of the pulse allows determining reliable field-dependent amplitudes of Fourier components with frequencies up to several kiloteslas. The Fourier spectrum is in agreement with the model of a linear chain of coupled orbits. In this model, all the observed frequencies are linear combinations of the frequency linked to the basic orbit α and to the magnetic-breakdown orbit β.

A numerical method for describing the electrical response of a Back-Gated Metal-Semiconductor- Metal Photodetector (BGMSM-PD) to an impinging optical pulse on the active region of the device is presented. In the absence of external voltage, the main mechanism for the transport of photo-generated carriers is diffusion mechanism. Two nonlinear differential equations describe the behavior of photocarriers’ densities in the device medium with respect to time and position. Having linearized the parabolic partial differential equations, the time evolution of carrier densities is calculated using the Alternating Direction Implicit (ADI) method. The numerical results show good agreement with the experimental data. Both experimental and numerical findings confirm that the electrical response of the device to optical pulses with spatial FWHM comparable with the width of the active region is dependent on pulse position on the active region. This feature of the device makes it to be a good candidate as position sensors in places where micro-positioning is required.

AlN films of thicknesses 670–780 nm were deposited on (1 1 1) silicon wafer, (0 0·1) sapphire, float glass and fused silica substrates by reactive mid-frequency (41 kHz) ac sputtering of dual hollow Al targets in a mixture of Ar and N2 gases. Nanostructured films of hexagonal wurtizite phase of AlN were prepared and characterized by UV-visible spectroscopy and X-ray diffraction. The novel geometry of dual target inverted cylindrical magnetrons produces very dense plasma and ion bombardment of the growing film, and facilitates the formation of highly crystalline AlN coatings without any deliberate substrate heating. Substrates showed significant influence on the crystal structure of AlN films; sapphire forms hexagonal AlN phase with very strong texturing toward (0 0·2) crystallographic orientation, silicon wafer grows small amount of metastable high-pressure cubic phase of AlN along with the predominant, thermodynamically stable hexagonal phase while the amorphous glass substrates form hexagonal AlN phase with a random orientation of the crystallites.

The electronic charge transport in active layer of organic thin-film transistor (OTFT) based on conductor polythiophene (sexithiophene (6T) and octithiophene (8T)) was studied. A mathematical model is presented based on the variable range hopping (VRH) transport theory. Using the VRH model the expression of source-drain current is established for two regimes: linear regime for drain bias VD = −2 V and saturation regime for VD = −30 V at low temperature and at room temperature. All electrical key parameters of OTFTs based on polythiophene have been extracted. A good agreement between theoretical model and experimental measurement of electrical characteristics is obtained for both temperature ranges: low temperature and room temperature.

We propose the spot-size effect in laser-induced damage to optical thin films as a method to investigate the defect removal model which is one of the laser conditioning mechanisms, and the theoretical and experimental studies are presented. A standard deviation σ2 is set up for fitting the damage thresholds which are obtained by multi-spot size test. The laser conditioning effect on ZrO2/SiO2 multilayer high reflective films is analyzed through this application. It is found that the mean distance of two initiating defects is increased by laser conditioning, which means that the defect density is decreased. Thus, the initiating defects are removed partially by laser conditioning. Furthermore, the intrinsic damage threshold of the film is little affected through the laser conditioning process.

The fabrication of Al-pSnSe Schottky diodes and the temperature dependence of I-V characteristics in the temperature range 60 < T < 330 K have been studied. A decrease in the experimental barrier height Φap and an increase in the ideality factor n with a decrease in temperature have been explained based on barrier height inhomogeneities at the metal-semiconductor interface. It is proven that the presence of a distribution of barrier heights is responsible for the apparent decrease of the zero-bias barrier height. The voltage dependence of the standard deviation causes the increase of ideality factor at low temperatures. The mean barrier height Φbmean = 0.851 eV and the Richardson constant A* = 10.26 A cm−2 K−2 have been calculated by means of the modified Richardson plot. The value of the Richardson constant found is much closer than that obtained without considering the inhomogeneous barrier heights with that of the theoretical value.

Pure iron nanoparticles (NPs) are fabricated using a simple and low-cost electric arc-discharge method in ethylene glycol (EG). The effect of different arc discharge currents (10, 20 and 30 A) on the size and optical absorption of the NPs is studied. Dynamic light scattering (DLS) and UV-visible spectroscopy data indicate that at the arc current of 10 A, the size of the particles is about 103 nm, and it can raise the arc current leading to larger NPs. UV-visible spectroscopy data show that the solvent gets more and more transparent with time, an effect which, sonication, proves that is related to agglomeration of the NPs. The evidence of pure Fe NPs is investigated by means of X-ray diffraction (XRD) measurement the average size of which is about 14 nm using Scherrer’s relation. Magnetization measurements of the samples are carried out by alternating gradient force magnetometer (AGFM). These results have shown that the arc discharge method is an effective method for preparing magnetic fluids in one step and EG is the effective medium for caring Fe NPs against oxidation. Therefore, the method can pave the way for the synthesis of other NPs such as Fe, Fe-Co, Fe-Pt and iron oxide.

Titanium nitride thin films have been grown on Si substrates by using DC reactive magnetron sputtering from a titanium target at different DC power (100–400 W). The different plasma parameters such as plasma potential, floating potential, electron temperature, electron density and ion density have been measured using a Langmuir probe. The electron energy distribution function (EEDF) has been evaluated from the second derivative of I-V plot of the Langmuir probe data and has shown to be bi-Maxwellian. The correlations between measured plasma parameters and the properties of TiN films deposited at the same operating conditions have been studied. It has been observed that the hardness decreases and the resistivity increases in films deposited at higher DC power. This is attributed to the growth of Ti2N phase at higher powers. The mechanical properties of the films have also been studied.

We propose a simple method to design multichannel electron wave filters based on graphene superlattices with one-dimensional periodic potentials, which can choose not only the peak energy of each channel but also the bandwidth independently. This method is described by two samples for the design of two-channel, three-channel filters. Additional defects are introduced symmetrically into the superlattices, then modes are generated, which overlap with the channels that need to tune. These defects make the bandwidth of a certain channel increased without location shifted, while the other channels almost keep constant. The corresponding electronic devices may benefit from this method.

Physical properties of pure bitumen 35/50 and polymer-modified bitumen 13/40 are studied using needle penetration test and differential scanning calorimetry (DSC). In particular, the mechanical response under indentation conditions is achieved as a function of different loads and temperatures. Our results show that lower temperature susceptibility is associated to larger loads but its change is rather small for the tested bitumens. A pure bitumen 35/50 exhibits a single glass transition temperature for different heating rate whereas modified bitumen 13/40 presents two Tg for different heating rate.

Gold nanoparticles have great potential toward optical investigations in biological tissues which include imaging applications as well as therapeutic applications. However, introduction of gold nanoparticles such as nanospheres into the tissue may alter the inherent physical properties of the embedding medium. Of note, the thermal diffusivity of the medium will be significantly altered imposing serious limitations to the efficacy of several imaging and therapeutic modalities. In this context, we report experimental investigations based on open photoacoustic cell configuration to evaluate the thermal diffusivity changes in polyvinyl alcohol (PVA) phantom tissue doped with gold nanospheres. The investigations performed demonstrate a non-destructive methodology for the measurement of thermal diffusivity and the experimental results show that the thermal diffusivity of the tissue will be significantly reduced when they are administered with plasmonic nanoparticles.

The effect of dc magnetic field on the capacitance, impedance and resistance of Dy2.8Sr0.2Fe5O12 (DySrIG) prepared using the citrate-nitrate auto-combustion method was studied at room temperature. The measurements were carried out in two ways; the first one in which the dc magnetic field and the ac electric field are parallel (//) to each other and the second one in which the magnetic field and ac electric fields are perpendicular (⊥) to each other. The magnetoimpedance of Dy2.8Sr0.2Fe5O12 increases by about 80% in the (⊥) case (at 1650 Oe and 450 kHz) with respect to its values at zero magnetic field. The results of the study encourage the use of this garnet nanomaterial in magnetic sensors, in new devices including tunable filter and spintronic applications.

Amorphous thin films of Se100 − XSbX (X = 1, 5, 10, 15 and 20) were synthesized by flash evaporation of the premelt quenched bulk samples. The optical properties were investigated from spectrophotometric measurements in the UV-VIS-NIR spectral region using Swanepoel’s standard envelope method and related techniques. The optical band gap energy (Egopt) was evaluated from the Wemple-Didomenico (WDD) single oscillator model and Tauc’s extrapolation method in the region where the absorption coefficient, α ≥ 104 cm–1. The observed values of Egopt and oscillator energy Eo were found to decrease monotonously with increasing Sb additive. The complex dielectric constant (ε), Urbach energy (Eu), optical conductivity (σ), plasma frequency (ωp) and lattice dielectric constant (εL) were deduced for each alloy composition. The complex refractive index (n) fitted well to Sellmeier function which can allow extrapolation of n outside the measured spectral range. The observed changes in optical parameters with Sb content were explained on the basis of increased defect states and changes in cohesive energy indicators (average heat of atomization (Hs), mean coordination number 〈Z〉 and average single bond energy (Hs/〈Z〉).

The minibands and minigaps in the transmission bands of one-dimensional photonic crystals have been studied through Bloch’s theorem, the tight-binding method and calculations based on the transfer matrix method. The minigap depths are dependent on the resonance intensity within the layers of one-dimensional photonic crystals and can be manipulated through the incidence angle. For a special structure and incidence angle, a polarization-independent flattop band can be achieved.

This paper presents a novel preparation of copper (Cu) deposited titanium dioxide (TiO2) nanotubes in photoelectrochemical systems. The main target was improving TiO2 applications in the areas of energy conversion under visible light. Herein, we investigated different amount of Cu deposited TiO2 nanotubes using thermal evaporation technique. Based on the results, small amount of Cu (1.09 wt.%) showed the improvement in photoelectrochemical (PEC) response under visible light. Optimum amount of Cu deposited on TiO2 nanotubes will inhibit recombination rate of photogenerated charge carriers and improve the charge separation and transfer under visible light illumination. However, the excess amount of Cu deposited on TiO2 nanotubes will impede the photocurrent to flow and resulted in lower photoconversion efficiency. The reason may be attributed to the formation of composite structure on TiO2 nanotubes that serve as defects in the Cu/TiO2 interface by the lattice mismatch that will serve as recombination site for the charge carriers.